The invention concerns a permanent magnet type stirrer drive for a high pressure autoclave, where the inner coupling part comprises the magnet shaft equipped with permanent magnets on the outside, the inner coupling part being covered by a hood, the outer coupling part comprising the magnet bell equipped with permanent magnets on the inside, the magnet bell covering the hood.
Such a stirrer drive is known and described by German GBM Pat. No. 1,897,029. The autoclave is closed at the top by a tubular pressure housing. The stirrer shaft bearing is arranged in the housing. In order to meet the requirement of a minimum possible gap between inner and outer magnets, the annular inner magnets are segmented upon the upward stirrer shaft extension and enclosed by the tubular housing which is thin-walled by virtue of its small diameter. In this type of arrangement, the average ratio of the ring magnet diameter to the stirrer shaft diameter is smaller than, or equal to 2.5, while the ratio of the total annular magnet width to the stirrer shaft diameter is larger than 8.
The annular magnets lined up on the stirrer shaft constitute a long shaft-like magnetic coupling for industrial stirrer drives. A bearing must necessarily be provided in the tubular housing for the upper end of the stirrer shaft segmented with magnets, since the shaft would otherwise come into contact with the tubular housing as a result of a possible unbalance and vibrations.
The driving motor is arranged above the magnetic coupling. Due to the length of such a coupling type, the tubular housing will not exhibit great rigidity. In order to avoid undesirable vibration, the motor housing must be attached to the cover of the high-pressure autoclave via supports.